Metal oxide matrix biosensors

Abstract

A thin film matrix for biomolecules, suitable for forming electrochemical and biosensors comprising a general class of materials known as hydrous metal oxides which are also conductive or semiconductive of electrons and which have been shown to have excellent stability against dissolution or irreversible reaction in aqueous and nonaqueous solutions. The composites are bifunctional, providing both amperometric and potentiometric (pH) transduction. The thin film composites of the oxides and biological molecules such as enzymes, antibodies, antigens and DNA strands can be used for both amperometric and potentiometric sensing. Hydrous Ir oxide is the preferred matrix embodiment, but conducting or semiconducting oxides, of Ru, Pd, Pt, Zr, Ti and Rh and mixtures thereof have similar features. The hydrous oxides are very stable against oxidation damage.

What I claim is: 
     
       1. An electrode useful in chemical sensing comprising: (a) an electrically conductive base material   (b) a thin film of a porous hydrous metal oxide conductive of both electrons and ions coated thereon and   (c) one or more substances disposed within said metal oxide, said substances possessing reactive recognition properties for one or more chemicals   wherein the hydrous metal oxide provides electrical contact between the electrically conductive base material and a product of said reactive recognition   said hydrous metal oxide being derived substantially from Ir, Ru, Pd, Pt, Zr, Ti and Rh, or mixtures thereof.   
     
     
       2. The electrode of claim 1 wherein said base material is Ir. 
     
     
       3. The electrode of claim 1 wherein said substances with reactive recognition properties interact with a chemical to produce a product that is electrochemically active between -0.6V and 0.8V versus an Ag/AgCl reference electrode. 
     
     
       4. The electrode of claim 1 obtained by electrochemical growth of the hydrous metal oxide on the parent metal in an electrolyte also containing said substances with reactive recognition properties. 
     
     
       5. The electrode of claim 1 obtained by electrochemical polarization of said hydrous metal oxide film in the presence of said substances with molecular recognition properties. 
     
     
       6. The electrode of claim 1 wherein said substance is an enzyme. 
     
     
       7. The electrode of claim 6 wherein the enzyme is an oxidoreductase enzyme. 
     
     
       8. The electrode of claim 7 wherein said oxidoreductase enzyme is glucose oxidase. 
     
     
       9. An amperometric biosensor having an electrode as recited in claim 1 incorporated into an electrochemical cell containing an electrolyte also containing the chemical to be sensed the products of said reactive recognition being detected and quantified by transferring electrons between said product and said hydrous metal oxide electrode and to an external circuit incorporating a current measuring means.   
     
     
       10. The amperometric biosensor of claim 9 wherein the current is greater than 10 microamps per cm 2  of electrode area. 
     
     
       11. The amperometric biosensor of claim 9 wherein said substance with reactive recognition properties is glucose oxidase, said chemical is glucose, and said products are gluconolactone and FADH 2  contained within the glucose oxidase said detection proceeding by direct electrochemical oxidation of FADH 2 .   
     
     
       12. The amperometric biosensor of claim 9 wherein said substance with reactive recognition properties is glucose oxidase, said chemicals are glucose and O 2 , and said products are gluconolactone and H 2  O 2   said detection proceeding by electrochemical oxidation of H 2  O 2 .   
     
     
       13. The amperometric biosensor of claim 9 wherein an inhibitor of said substance with reactive recognition properties is detected by a decrease in current response to the products of said reactive recognition. 
     
     
       14. A potentiometric biosensor having an electrode as recited in claim 1 incorporated in an electrochemical cell containing an electrolyte also containing the chemical to be sensed the products of said reactive recognition being detected by transferring protons or hydroxide to or from said hydrous metal oxide   the accompanying change in the potential of the hydrous metal oxide electrode being detected by an external circuit incorporating a voltage measuring means.   
     
     
       15. The potentiometric biosensor of claim 14 wherein the potential changes in less than 1 minute in response to a change in chemical composition of 100 mM. 
     
     
       16. The potentiometric biosensor of claim 14 wherein said substance with reactive recognition properties is acetylcholinesterase, said chemical is acetylcholine, and said products include acetic acid which protonates said hydrous metal oxide. 
     
     
       17. The potentiometric biosensor of claim 14 wherein an inhibitor of said substance with reactive recognition properties is detected by a decrease in voltage response to the products of said reactive recognition. 
     
     
       18. The potentiometric biosensor of claim 14 wherein said substance with reactive recognition properties is acetylcholine, said chemical is acetylcholinesterase, and said products include acetic acid which protonates said hydrous metal oxide. 
     
     
       19. The electrode of claim 1 wherein at least one of said substances with molecular recognition properties is an antibody. 
     
     
       20. The electrode of claim 1 wherein at least one of said substances with molecular recognition properties is a nucleic acid strand. 
     
     
       21. The electrode of claim 1 further containing an electron transfer mediator disposed within said hydrous metal oxide. 
     
     
       22. The electrode of claim 21 wherein said electron transfer mediator is ferrocene or a ferrocene derivative. 
     
     
       23. The electrode of claim 1 wherein said substances with reactive recognition properties are acetylcholinesterase and choline oxidase. 
     
     
       24. An amperometric biosensor for acetylcholine comprising the electrode of claim 23 incorporated into an electrochemical cell the choline product of the said reactive recognition between acetylcholine and acetylcholinesterase interacting with choline oxidase to form betaine and a reduced product   said detection proceeding by electrochemical oxidation of the reduced product.